HR: 0830h
AN: SA41B-0428    [PDF]
TI: Detection of Long-Term Variations in Neutral Thermospheric Density
AU: * Marcos, F A
EM: frank.marcos@hanscom.af.mil
AF: Air Force Research Laboratory VSBXT, 29 Randolph Road, Hanscom AFB, MA 01731-3010 United States
AU: Grossbard, N J
EM: neil.grossbard@hanscom.af.mil
AF: Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467-3862 United States
AB: A new database of thermospheric densities has been derived for the period 1970 - 2000 from satellite orbital decay analysis. The data are generated from actual radar tracking observations, rather than from the less accurate historical element sets, to form precise orbit and drag/density data with improved accuracy and one-day resolution. Satellites with relatively high eccentricities were used to achieve long lifetimes and relatively localized latitude and local time resolution. We analyze data from six satellites with an average altitude of about 350 km. Data are compared to three empirical models (Jacchia, NRLMSIS and NASA MET). The data are normalized to remove systematic model errors vs solar activity detected in all three models. A linear regression fit through these normalized data is obtained for each satellite. The weighted average of these fits show a downward trend of 5.2 percent over 30 years with a 95 percent confidence interval of 1.1 percent. The results are analyzed as a function of solar flux and compared to theoretical predictions. Possible dependencies on local time, latitude and geomagnetic activity are also examined. These results tend to confirm global cooling at satellite altitudes, possibly associated with increased carbon dioxide in the thermosphere.
DE: 0350 Pressure, density, and temperature
DE: 0355 Thermosphere--composition and chemistry
DE: 0358 Thermosphere--energy deposition
DE: 1600 GLOBAL CHANGE (New category)
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting